Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

30 Understanding Veritas Volume Manager
How VxVM handles storage management
■ striping (RAID-0)
■ mirroring (RAID-1)
■ striping with parity (RAID-5)
Concatenation, striping (RAID-0), mirroring (RAID-1) and RAID-5 are described in
“Volume layouts in VxVM” on page 32.
Vo l u m e s
A volume is a virtual disk device that appears to applications, databases, and file systems
like a physical disk device, but does not have the physical limitations of a physical disk
device. A volume consists of one or more plexes, each holding a copy of the selected data
in the volume. Due to its virtual nature, a volume is not restricted to a particular disk or a
specific area of a disk. The configuration of a volume can be changed by using VxVM
user interfaces. Configuration changes can be accomplished without causing disruption to
applications or file systems that are using the volume. For example, a volume can be
mirrored on separate disks or moved to use different disk storage.
Note: VxVM uses the default naming conventions of vol## for volumes and vol##-##
for plexes in a volume. For ease of administration, you can choose to select more
meaningful names for the volumes that you create.
A volume may be created under the following constraints:
■ Its name can contain up to 31 characters.
■ It can consist of up to 32 plexes, each of which contains one or more subdisks.
■ It must have at least one associated plex that has a complete copy of the data in the
volume with at least one associated subdisk.
■ All subdisks within a volume must belong to the same disk group.
Note: You can use the Veritas Intelligent Storage Provisioning (ISP) feature to create and
administer application volumes. These volumes are very similar to the traditional VxVM
volumes that are described in this chapter. However, there are significant differences
between the functionality of the two types of volume that prevent them from being used
interchangeably. Refer to the Veritas Storage Foundation Intelligent Storage Provisioning
Administrator’s Guide for more information about creating and administering ISP
application volumes.
In Figure 1-10, volume vol01 has the following characteristics:
■ It contains one plex named vol01-01.
■ The plex contains one subdisk named disk01-01.